Method of finishing textile fabric prepared from polyester blend yarns, and resulting fabric



Sept. 13. 1966 R. "r. STIEHL 3,

METHOD OF FINISHING TEXTILE FABRIC PREPARED FROM POLYESTER BLEND YARNS, AND RESULTING FABRIC Filed Sept. 12, 1961 POLYESTER BLEND FABRIC I TREAT AT 10-1200. mm AQUEOUS SOLUTION OF PH 0 CONTAINING EXCESS SOLID PARAFORNALOEHYOE RINSE APPLY CURING CATALYST SOLUTION HOLD TAUT NIIILE DRYING I HOLD TAUT WHILE cums u |4o-2s0c.

SUPPORT INVENTOR ROY T. STIEHL .x BY A? United States Patent 3,272,587 METHOD OF FINISHING TEXTILE FABRIC PRE- PARED FRQM POLYESTER BLEND YARNS, AND RESULTKNG FABRIC Roy T. Stiehl, Waynesboro, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed ept. 12, 1961, Ser. No. 137,553 5 Claims. (Cl. 8-1157) This invention relates to a method of finishing textile materials. More particularly, it relates to a novel method of imparting wrinkle resistance and dimensional stability to fabrics prepared from blended yarns containing synthetic polyester fibers.

It is well known to treat cellulosic and keratinic fibers with formaldehyde with the object of obtaining various effects. For example, as early as 1906, Eschalier in British Patent 25,647 disclosed a process for strengthening cellulose threads, films, and the like, which consists of impregnating the materials with a solution containing an aldehyde which may be formaldehyde, and an acid or acidreacting substance, and then treating under dehydrating conditions.

In recent years, voluminous literature has developed around the formaldehyde treatment of textile materials, a large part of it being devoted to the attainment of wrinkle resistance and dimensional stability. It is generally accepted that the eifects are produced by a crosslinking of the polymeric chains by form-aldehyde. Although it has been found that the degree of crosslinking increases as the concentration of formaldehyde increases and as the acidity of the treating solution increases, it has also been found that high concentrations of formaldehyde in very acid solutions result in excessive tendering of the fabric with a resultant loss of strength. Consequently, presently-accepted formaldehyde treatments for cellulosic and keratin-i0 textiles are built around solutions of moderate formaldehyde concentration and moderate acidity.

Wrinkle resistance, crease retention, and dimensional stability have also been imparted to cellulosic and keratinic textiles by blending the keratinic or cellulosic fiber with one of the new synthetic polyester fibers, such as those disclosed in US. 2,465,319 and US. 2,901,466. The outstanding performance of these blend fabrics has led to the commercial success of Wash-and-wear garments prepared from such fabrics. However, the stringent requirements for Wash-and-wear garments make it highly desirable that the wrinkle resistance and dimensional stability of polyester blend fabrics be increased to a still higher level. Prior fabric finishing procedures have not been successful in achieving this result.

It is an object of this invention to provide textile fabrics from blended polyester yarns which have a higher degree of wrinkle resistance, and dimensional stability than has hitherto been obtained. Another object is the provision of textile fabrics prepared from polyester-cellulo-sic, polyester-keratinic, and polyester-polyamide blended yarns wherein the cellulosic, keratinic, and polyamide fibers are crosslinked with formaldehyde. A still further object is the provision of a process for treating polyester blend fabrics with formaldehyde wherein an outstanding improvement in performance is obtained without appreciable loss of strength.

Unexpectedly it has been found that textile fabrics prepared from poylester blends may be treated with highly acid solutions containing high concentrations of formaldehyde without substantial loss of strength, and that the resulting fabrics exhibit a performance level in wash-and-wear garments higher than any fabrics known heretofore.

3,272,587 Patented Sept. 13, 1966 ice Accordingly, the objects of this invention are attained by a process for treating textile fabrics prepared from polyester blend yarns containing 4580% polyester fiber and 20-55% of a fiber capable of being crosslinked with formaldehyde comprising treating the fabric at a temperature of 70120 C. with an aqueous solution of formaldehyde having a formaldehyde concentration of at least 40% and having a pH no greater than 0.5, rinsing the fabric with water until free of unreacted formaldehyde and acid, applying to the fabric catalyst solution which is essentially an aqueous solution of a non-volatile, noncharting acid, applying suflicient tension to the wet fabric to prevent shrinkage greater than 5% in any direction, drying the fabric in this taut condition, and then heating the dried fabric, under tension, at a temperature of 140 230 C. to complete the curing reaction.

The term polyester blend yarns refers to yarns prepared from blended staple in which at least 45% by weight of the staple is composed of fibers prepared from synthetic linear condensation polyesters, or to composite yarns of the same relative composition prepared from continuous filaments. These polyesters are prepared by the polycondensation of ester-forming monomers according to processes and procedures known to the art.

The term synthetic linear condensation polyester, as used herein, comprehends a substantially linear polymer of fiber-forming molecular weight comprising a series of predominantly carbon atom chains joined by recurring divalent ester radicals, each of said ester radicals comprising a carbonyl group attached on at least one side to an oxygen atom. The divalent ester radicals may be represented by the general formula where j and k are 0 or 1 and j+k=1 or 2. As used herein, the term polyester is intended to include copolyesters, tel-polyesters, and the like.

In a preferred embodiment of the invention, the fiberforming polymer is a synthetic linear condensation polyester of bifunctional ester-forming compounds wherein at least about of the repeating structural units of the polymer chain include at least one divalent carbocyclic ring containing at least six carbon atoms present as an integral part of the polymer chain and having a minimum of four carbon atoms between the points of attachment of the ring in the polymer chain (para-relationship in the case of a single 6-membered ring). The polyesters may be derived from any suitable combination of bifunctional ester forming compounds. Such compounds include hydroxy acids such as 4-( 2-hydroxyethyl)benzoic acid and 4-(2-hydroxyethoxy)benzoic acid, or mixtures of the various suitable bifunctional acids or derivatives thereof and the various suitable dihydroxy compounds and derivatives thereof. The repeating structural units of the polymer chain comprise recurring divalent ester radicals separated by predominantly carbon atom chains comprising hydrocarbon radicals, halogen-substituted hydrocarbon radicals, and chalcogen-containing hydrocarbon radicals wherein each chalcogen atom is bonded to carbon or a different chalcogen atom, and no carbon is bonded to more than one chalcogen atom. Thus, the repeating units may contain ether, sulfonyl, sulfide, or carbonyl radicals. Sulfonate salt substituents may also be present in minor amount, up to about 5 mol percent total sulfonate salt substituents .in the polyester based on the number of ester linkages present in the polyester. Other suitable substituents may also be present.

Among the various suitable dicarboxylic acids are terephthalic acid, bromoterephthalic acid, 4,4'-sulfonyldibenzoic acid, 4,4-diphenic acid, 4,4-benzophenonedicarboxylic acid, 1,2-bis(4-carboxyphenyl)ethane, 1,2-bis J (p-ca'rboxyphenoxy)ethane, bis 4 carboxyphenyl ether and various of the naphthalenedicarboxylic acids, especially the 1,4-, 1,5-, 2,6-, and 2,7-isomers. Isophthalic acid is also suitable, especially when used in combination with a 1,4-dihydroxy-aromatic compound. Carbonic acid is similarly suitable.

Among the various suitable dihydroxy compounds are the glycols, such as ethylene glycol and other glycols taken from the series HO(CH OH, where n is 2 to 10; cisor trans-p-hexahydroxylylene glycol; diethylene glycol; quinitol; neopentylene glycol; 1,4-bis(hydroxyethyl) benzene; and l,4-bis(hydroxyethoxy)benzene. Other suitable compounds include dihydroxyaromatic compounds such as 2,2-bis(4-hydroxy-3,S-dichlorophenyl) propane, 2,2 b-is(4 hydroxyphenyl)propane, hydroquinone, and 2,5- or 2,6-dihydroxynaphthalene.

The polyester blend yarns of this invention also contain one or more fibers from the group consisting of cellulose, -keratinic, and polycarbonamide fibers. By cellulose fiber is means both the naturally occurring cellulose fibers such as cotton, and regenerated cellulose fibers such as rayon. By keratinic fibers is meant the naturally occurring protein fibers such as wool, as well as fibers derived from protein material. By polycarbonamide fibers is meant fibers prepared from synthetic polyamides such as polyhexaimethylene adip-amide and p'olycaproamide. Commercially important examples of blends of these classes include polyethylene terephthalatecotton blends, polyethylene terephthalate-rayon blends, polyethylene terephthalate-wool blends, and polyethylene terephthalate-nylon blends.

Each step in the process of this invention as described herein is essential for the attainment of the objectives of this invention. It is also essential that the steps be carried out in the order given.

The first step of the process is the treatment of the polyester blend fabric with the formaldehyde solution. The step may be carried out on greige fabric, but better results are obtained if the fabric has been prescoured. It is necessary that the formaldehyde solution contain at least 40% formaldehyde, and that the pH of the solution be less than 0.5, preferably or lower. Thus, the

- formaldehyde solution may be prepared from commercially-available 5 0% formaldehyde solutions by adjusting the pH of the solution. Commercially-available 37% formalin solutions may be used if additional formaldehyde is added to raise the concentration above 40%. Methanol or other aliphatic alcohols may be present to stabilize the formaldehyde solution in the conventional manner.

In a preferred embodiment of the invention, the formaldehyde solution is prepared by adjusting the pH of the water bath to a value less than 0.5, preferably 0 or lower, and then suspending in the bath sufficient solid paraformaldehyde such that the formaldehyde solution formed is in equilibrium with an excess of solid paraformaldehyde at the reaction temperature. The solution thus has I a formaldehyde concentration of at least 4050%, the

actual concentration being dependent upon the tempera- The fabric being treated is contacted with the formaldehyde solution for a period of at least 5 seconds at a temperautre of 70-150 C. A temperature of 80-l00 C. is preferred. The higher treating temperatures require shorter treating times for the attainment of the desired results. The treatment may be carried out for as long as 1 or 2 hours, but long treating times are uneconomical and are not recommended.

The pH of the formaldehyde solution may be adjusted with any strong, soluble non-oxidizing acid. Suitable acids include, for example, sulfuric acid, phosphoric acid, hydrochloric acid, and trifiuoroacetic acid. Oxidizing acids such as nitric acid and perchloric acid generally result in fabric degradation and are not recommended.

The treatment of the fabric with the formaldehyde solution may be carried out in any suitable vessel. For example, the treatment may be carried out in a beck, jig, autoclave, or in other suitable textile finishing equipment. A closed system is preferred because of the volatility and toxicity of formaldehyde.

Alternatively, the fabric may be wet out with the formaldehyde solution at a lower temperature, i.e., 20- 100 C., squeezed out to give a wet pickup in the range 130%, and then placed, wet, between neoprene-coated Fiberglas (trademark of Owens-Corning Fiberglas Corp.) sheets, or their equivalent, for the heating step. The fabric sandwich is heated in any of several convenient ways, e.-g., by running the sandwich over a series of heated rollers, or through a semi-decator, or by running it through a heated oven. Heating times as short as 5 seconds may be used at the upper end of the preferred temperature range.

After the impregnation of the fabric with the acidified formaldehyde solution, the next step is the removal of unreacted formaldehyde and acid from the fabric by a water rinse. A thorough rinse prevents charring during the subsequent heating step, as well as preventing the evolution of noxious formaldehyde fumes. Either hot or cold water may be used in the rinse, although cold water is preferred in order to minimize hydrolysis reactions.

The rinsed fabric is then contacted with an aqueous solution containing as a curing catalyst a non-volatile, non-charring acid. By non-volatile acid is meant an acid which has a boiling point above 230 C. By noncharring acid is meant an acid which, in the concentration used, does not cause charring of the cellulosic or keratinic fiber during the heating step which follows. Suitable acids include phosphoric acid, hypophosphorus acid, sulfuric acid, p-toluenesulfonic acid, and citric acid. A sufficient quantity of the acid catalyst solution is applied to the fabric to give a pickup of 0.020.5 weight percent acid based upon the weight of non-polyester fiber in the fabric. Thus, for example, a suitable procedure might use a 0.1% phosphoric acid solution at the wet pick-up level on a fabric containing 50% polyester fiber.

After applying the acid catalyst, the wet fabric is then placed under sufiicient lengthwise and widthwise tension to substantially prevent shrinkage during the drying step. This step may be conveniently carried out on a clip or pin tenter, or other suitable framing device. It is essential that the fabric be kept taut during the drying step in order to prevent wrinkles and to obtain the desired improvement in wrinkle resistance. The drying operation is accelerated by heating the fabric to an elevated temperature.

After drying, the fabric is heated, still under tension,

- to a temperature of -230 C. for a period of 0.5-5.0

minutes in order to complete the formaldehyde crosslinking action. Shorter curing times are required at the higher temperatures. Long curing times are to be avoided in the case of polyester-wool blend fabrics since the heat treatment tends to yellow the wool.

In a preferred embodiment of this invention, the treated fabric is woven from spun yarns containing synthetic linear polyester fiber and fiber of cellulosic origin such as cotton or rayon. The concentration of polyester fiber in the spun yarn may range from 45-80%. A preferred spun yarn is one in which the ratio of polyester fiber to cellulosic fiber is about 65 to 35. After treatment with formaldehyde according to the process of this invention, the amorphous regions of the cellulosic fiber are found to contain concentrations of bound formaldehyde in the range 6 to 9%. The fabric is characterized by a boil-off shrinkage of less than 2%, and is further characterized by an increased fabric bending modulus amounting to at least 1.5X where X is the bending modulus of the untreated fabric.

It is to be understood that the blended yarn containing 45-80% polyester fiber may be found in either the warp or the filling, or in both warp and filling, in the fabrics of this invention. It is also to be understood that the advantages of this invention accrue also to knitted and non-woven fabrics.

Bending modulus, as used herein, refers to the average bending modulus, in gm./cm. defined by the equation:

where Q is the bending modulus in the warp direction and Q is in the filling direction. The filling and Warp moduli are calculated from where In the drawing FIG. 1 is a diagrammatic sketch of a device for determining the bending length. FIG. 2 is a self-explanatory flow sheet.

To find bending length, C a fabric strip is cut to a size of about /2" by 1 /2" and clamped at one end in a horizontal position as in FIGURE 1. The length extending from the clamp is measured exactly and designated L. The unclamped end of the sample is then allowed to hang freely, and the vertical and horizontal distances from the free end to the clamp jaws measured and designated y and x, respectively. Using the measured values of L, x, and y, the value of C is calculated from the following relationships:

2 =o' cos 0 and g=0 where 0 is the inclination angle shown in FIGURE 1;

50:]: cos Qda and y=jg sin fida; and a=tarr A solution is readily found using a computer and the Runge-Kutta method of approximation. The results are conveniently plotted in the form of a graph of versus a which enables values of C to be read off for any value of oz, when L is known.

The formaldehyde content of the cellulosic fiber may be conveniently determined by the following procedure:

A carefully weighed sample is hydrolyzed with acid to convert all of the bound formaldehyde to the monomeric form. Chromotropic acid is then added to form a complex with the formaldehyde and the concentration of the complex determined colorimetrically.

When the fabric of this invention is subjected to a series of simulated home launderings involving a standard machine wash followed by tumble drying, wrinkle resistance is found to be nearly perfect. The fabric emerges from the wash-dry cycle with the appearance of having been freshly ironed.

In another embodiment of this invention, the fabric to be treated with formaldehyde is prepared from yarn spun from a blend of polyester and wool fibers in which at least 40% of the fiber is polyester fiber and in which at least 20% of the fiber is wool. The formaldehydetreated fabric is found to have not only greatly improved recovery properties and increased liveliness but also a high degree of stabilization toward felting, a necessary feature of wash-and-wear wool blend fabrics.

An important feature of this invention is the fact that the formaldehyde-treated fabrics can be framed to the desired width during the formaldehyde curing process and will retain this width during the remainder of the usual commercial finishing treatments for such fabrics. Thus, working loss during mill processing is essentially eliminated.

The following examples are cited to illustrate some of the many embodiments of this invention.

Example I A treating bath is prepared by adding 92 parts of concentrated sulfuric acid to 1000 parts of water, giving a pH of 0, and then adding with stirring 750 parts of paraformaldehyde. A madras fabric, woven from 65/35 polyethylene terephthalate/viscose rayon spun yarn, is immersed in the solution, the container is sealed, and the temperature of the solution is raised to C. for a period of 30 minutes. The fabric is then removed from the formaldehyde solution and rinsed in cold water until free of the odor of formaldehyde. The rinsed fabric is then immersed in a solution containing 4 parts of phosphoric acid per 3000 parts of water. Excess liquid is allowed to drain off for about 30 seconds, giving about wet pick-up. The wet fabric is then pulled very tautly on a frame and held in the taut condition while being dried in an oven heated to 200 C. After drying the fabric is heated an additional 1 minute at 200 C. to complete the curing process.

The treated fabric is analyzed for bound formaldehyde and it is found that the amorphous regions of the rayon fibers contain 6.9% formaldehyde. When subjected to boil-off shrinkage tests, the fabric is found to have a residual shrinkage of 1.01.5%. Measurement of the bending modulus of the fabric reveals that the formaldehyde treatment has resulted in an 80% increase in bending modulus. The treated fabric has a bending modulus of 45 10 gm./cm. compared with a modulus of 26 for the untreated fabric.

A sample of the fabric is subjected to a simulated home laundry treatment in which the sample is given a standard machine wash followed by tumble drying. The fabric emerges essentially wrinkle-free from this treatment whereas a similar fabric which was not treated with formaldehyde according to the process of this invention was noticeably wrinkled after such a wash-dry cycle.

Example 11 A fabric treating bath is prepared by adding 92 parts of concentrated sulfuric acid to 1000 parts of water, giving a pH of 0, and then adding with stirring 800 parts of paraformaldehyde. A broadcloth shirting fabric woven from 65/35 polyethylene terephthalate/ cotton spun yarn is immersed in the solution, the container is sealed, and the temperature of the solution is raised to 80 C. for a period of 30 minutes. The fabric is then removed from the formaldehyde solution and rinsed in cold water until free of the odor of formaldehyde. The rinsed fabric is immersed in a solution containing 4 parts of 85% phosphoric acid per 3000 parts of water and allowed to drain to about 130% wet pick-up. The wet fabric is then pulled to a taut condition on a frame and held in the taut condition while being dried in an oven heated to 200 C. After drying, the fabric is heated an additional minute at 200 C. to complete the curing process.

The treated fabric is analyzed for bound formaldehyde and it is found that the amorphous regions of the cotton fibers contain 6.6% formaldehyde. When subjected to boil-off shrinkage tests, the fabric is found to have a residual shrinkage of 1%.

A sample of the fabric is subjected to a series of simu lated home laundry treatments in which the sample is given a standard machine wash followed by tumble drying. The fabric emerges essentially wrinkle-free from this treatment, even after ten washes, whereas a similar Example III A worsted fabric woven from /50 polyethylene terephthalate/wool spun yarn is treated for 30 minutes at a temperature of C. with an aqueous solution having a pH of 0, adjusted with sulfuric acid, and having suspended in the solution an excess of solid paraformaldehyde. After this treatment, the fabric is washed with cold water until free of the odor of formaldehyde. The fabric is then wet out with a solution containing 4 parts of phosphoric acid per 3000 parts of water. The wet fabric is pulled taut on a frame and held in the taut condition while being dried in an oven heated to 200 C. After drying, the fabric is heated an additional 3 minutes at 200 C. to complete the curing process.

After ten washings and dryings in home laundry equipment, the treated fabric is found to have no residual shrinkage. When worked in a wet condition, the treated fabric is found to be highly resistant to felting whereas an untreated fabric exhibits noticeable felting with an accompanying loss in fabric dimensions.

A sample of the fabric is subjected to simulated home laundry treatments, as in Example I, and shows an improvement in resistance to wrinkling, compared to an untreated control fabric.

Example IV A plain weave fabric woven from 67/33 polyethylene terephthalate/ 66 nylon filament yarns is treated with formaldehyde according to the procedure of Example I with the exception that the treatment is carried out at C. for a period of 30 minutes. The fabric is rinsed free of the odor of formaldehyde in cold water and then wet out with a solution of 4 parts of phosphoric acid per 3000 parts of water to about wet pick-up. The fabric is then dried on a pin frame under sufiicient tension to prevent shrinkage at a temperature of 200 C. After drying, the fabric is further heated for an additional minute at 200 C., under tension, to complete the curing process. Samples of the treated fabric are subjected to simulated home laundry treatments according to Example I. It is found that the treated fabric is substantially wrinkle-freeafter the washing treatment whereas a similar fabric, not treated with formaldehyde, was noticeably wrinkled after the washing treatment.

Similar results are obtained using fabrics in which the 66 nylon fibers are replaced by 6 nylon fibers prepared from polycaproamide.

Example V A batiste shirting fabric woven from 65/35 poly- (p-hexahydroxylylene terephthalate)/cotton spun yarn is treated with formaldehyde according to the procedure of Example I. A sample of the fabric is subjected to a series of simulated home laundry treatments as in Example I. The formaldehyde-treated sample emerges essentially wrinkle-free from this treatment, whereas a similar fabric which was not treated with formaldehyde is noticeably wrinkled after such a treatment.

Example VI Polyester blend fabric samples are treated with formaldehyde using a variety of treating conditions, as summarized in Table I. The treated samples are evaluated for performance characteristics, with the results shown in the table. In the table, the notations PT/R, PT/W, and PT/C refer to blends of polyethylene terephthalate fiber with rayon, wool, and cotton, respectively. Paraformaldehyde is abbreviated Pf. Broadcloth is abbreviated Bcloth." The curing catalyst concentration given in the table is based upon the non-polyester fiber in the blend.

TABLE I Fabric Sample No.

HCHO Solution Treatment Blend Excess Pf Acid pI-I Temp., C. Time Test samples:

Madras.

B cloth Madras formalin plus Pl (Yes).

30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min.

10 min. 10 min. 30 min. 30 min. 2 min.

5 min.

15 min. 30 min. 30 min. 30 min.

o OCDCQOONDO OQOOOOOO 30 min.

30 min. 30 min. 24 hrs.

30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min.

OQDOQOOCOCOQOOOOCD TABLE I-Continued Curing Catalyst Curing Condition Sample No. Test Results Agent Cone. Tension Temp, C. Time, min.

Test samples:

1 200 5 Wrinkle recovery, excellent.

200 5 Do. 200 5 Do.

180 5 Do. 200 5 D0. 200 5 Do. 200 5 D0. 200 5 Do. 200 5 Do. 200 5 D0. 200 6 Do. 200 5 Do. 200 5 Do. 200 5 D0. 200 5 Do. 200 5 D0. 200 5 Do. 200 5 D0.

200 5 Wrinkle recovery, unimproved. 100 5 Do. 200 5 Do. 200 5 Do. 200 5 Wrinkle recovery, slightly improved. 200 5 Wrinkle recovery, unimproved. 200 5 Fabric charred.

200 5 Wrinkle recovery, unimproved.

200 5 Fabric charred.

200 5 Wrinkle recovery, unimproved. 200 5 Fabric charred. 200 5 Wrinkle recovery, slightly improved. 200 5 Fabric charred. 200 5 Wrinkle recovery, unimproved. taut: cured 200 4 Fabric badly wrinkled after laundering. 200 5 Wrinkle recovery, unimproved. 200 5 Fabric felted during laundering. 200 5 D0.

The indication excess paraformaldehyde means that perature. The treated samples are tested for shrinkage an excess of solid paraformaldehyde was present in the solution, so that an equilibrium concentration of formaldehyde in the range 50% was achieved.

The formaldehyde treatment of Sample 19 is carried out with 15% isopropyl alcohol in the formaldehyde solution.

The curing catalyst concentrations of Samples 23 through 28 are given in terms of the pH of the catalyst solution. In applying the catalyst solution to the sample, the wet pick-up of Samples 23 and 24 was 130%; that of Samples 25, 26, 27, and 28 was The test results are given in terms of Wrinkle recovery which refers to the ability of a fabric to recover from wrinkling in a wash-tumble dry cycle. The data clearly indicate the superior performance achieved by the invention defined herein.

Example VII Fabric samples are treated according to the following formaldehyde solution, rinsed, a catalyst solution is applied, and then the sample is cured at an elevated tern during laundering, for bending modulus after treatment, for loss of strength during treatment, and for ability to recover from wrinkling in a wash-tumble dry cycle as summarized in Table II. Wrinkle recovery results are coded as follows:

E=Excellent (essentially as ironed) P=Poor (essentially as a cotton fabric after machine washing and tumble drying) Other abbreviations are the same as those in Table I of Example VI. Where the table indicates no excess of paraformaldehyde is present, it is to be assumed that the formaldehyde concentration is less than 40%.

The curing catalyst concentrations for samples 12 through 17 are given in terms of the pH of the catalyst solution. For these samples, wet pickup was 50%.

The data in Table II clearly indicate the critical selection of reaction variables necessary for the successful operation of the process of this invention.

TABLE II wwwwwmm wmmmwmwwwmwmmwwwm mmwww w y u ma E E EGGEEEG FFFPPPPP .1 k m mm H r y e e m I .1 T h t 5 086657543737584 7 4 670-383-372 n-U558850 mrmm 00000000000000000000000000 00000 U e o g P D m FJ442515098442951 3 0 07-39441 20180086 m e 44444444334 4 4344 4 4 4333444 333134 22 m T u mw 1 e1 m n e 00050000000000000000000000 01200 0 n n W 5545465446455646 5 6 41243440 22223403 0 H g i I. n p mmm AaAjAjAsasejjeAj h A h z l 3232203 u M 1 .l r. o S 0 r H w m i 0 n n h h H d u n 5 555555555555555 5 5 35055555 555555 m u n 1 i 4 4 A 0 0 o m s S S e 2 2 2 0 H H H N n m n n n u m c w m wmmmwmm wwmwmm H n n n u n o 2 2 "6x11220422 222222 o m u n m m 0 m c g l X s n m m m E mumnwnnwwwwwwwwnwwmwnwnwnw m m m T c n u u n u n o n n n n 555555555555555555555mv0500 5 5 O O 0 O 0 BBBBBBBBNBBBBBBBBBBBBMHBMfl fi H n d d d d d 55555555555555555555500500 5 5 6 u e 1 m T n n n u u R n U n n n Q n n n n bees s n 0 a a a a o a m a 5% 0 0.2222 2 2 a n n n h o WU Z WWWZ 2WW H H W n h n n t .22222222fi 3pppp D o. n c h a s m h m m w m m m n m u m m m m 0 8 H H a .1 t F B RRR 00 R 2 H u n n a a n u n 0 o o TTT TT T g u n u u s s n h n PPP PP P .m t n h n u h u u u e 0 g A n u F n u n e u n n n e n p A. A 4 A A A A. 4 44 A A. O. y m 0000000 0 a a 0 0000 d T r d r PPPPPPP S H H P PPPP d s d aa saaa z a 3333 u m n m HHIHHHH H C C H HHHH u .2 n u h n n n u n n u n n n n w u u n n u o o n n n n 1 u h n n u N a u n N u e 0 n n n n m n u n n m n m n e m n n n u a m s 1 s m D m m a m m a u u a m u u n n n u H S S 7 901234 a t Mfifi wfl m 1 23 4.nfl7 m U B m 2 233333 S s n] s n 6 0D. 8 0 T o T 0 rium and then cooled to room temperature. A 65/35 Example VIII A formaldehyde solution is prepared by adding 300 grams of isopropyl alcohol to 1700 grams of water conpolyethylene terephthalate/rayon Madras shirting fabric is wet out in the formaldehyde solution and drained for 30 seconds to give a wet pickup of 130%. The wet fabric taming sufiiclent sulfuric acid to give a pH of 0, and then i i d between two Sheets of neoprene and placed on stirring in 2000 grams of solid paraformaldehyde. The a C. metal plate for a period of 30 seconds, the fabric mixture 1s heated to C. for 2 hours to achieve equilib- 7 is removed, rinsed thoroughly, and then wet out in a solu- 13 tion of 0.1% phosphoric acid. The wet fabric is then mounted on a frame in a taut condition and heated to 200 C. for 6 minutes for drying and curing.

The formaldehyde treated fabric is tested for washwear performance in the home laundry treatment of Example I and is given a rating of excellent.

Although the specific examples have been described with reference to blends of certain specific polyester fibers, it is to be understood that any other linear condensation polyester fiber may be substituted in the examples with substantially equivalent results.

From the foregoing general description and detailed specific examples, it will be evident that this invention provides a novel process capable of producing superior textile fabrics woven from blended polyester yarns. These fabrics are characterized by excellent dimensional stability and wrinkle resistance, as well as outstanding shape retention and improved fabric liveliness. Furthermore, this improvement in properties is obtained without substantial loss in strength. The process may be carried out by the fabric finisher, using existing equipment and fabric-handling procedures, and thus a highly desirable improvement in fabric properties is obtained at low cost.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. In the process of treating with acid aqueous formaldehyde solution a textile fabric prepared from polyester blend yarns, the blend being a composite of to 80% synthetic linear condensation polyester fibers and 20% to fibers of the group consisting of cellulose, wool and nylon fibers, the improvement of wetting-out said fabric with at least 50%, based on the fabric weight, of a highly acid aqueous solution containing at least 40 parts formaldehyde per 100 parts by weight of solution and sufiiciently strong, soluble, non-oxidizing acid to have a pH of less than about 0.5, heating the wet fabric for a period of at least 5 seconds at a temperature of to 120 C., removing the unreacted formaldehyde and acid from the fabric, thereafter applying to the fabric a catalyst solution consisting essentially of a dilute aqueous solution of a non-volatile, non-charring acid and, while applying tension to the wet fabric to prevent more than 5% shrinkage in any direction, drying and then heating the fabric at a temperature between about 140 and 230 C. for about 0.5 to 5 minutes.

2. The process defined in claim 1 wherein said polyester fibers are glycol terephthalate polymer fibers.

'3. The process defined in claim 1 wherein said fabric is immersed in the aqueous solution containing formaldehyde and heated at a temperature between about and C.

4. The process defined in claim 1 wherein the catalyst solution is applied to the fabric to give a pick-up of 0.02 to 0.5 weight percent acid based on the weight of nonpolyester fibers in the fabric.

5. Fabric treated by the process defined in claim 1, the fabric containing from 6 to 9% by weight of bound formaldehyde in the amorphous regions of the non-polyester fibers, and being characterized by a boil-off shrinkage of less than 2% and by having a bending modulus as herein defined of at least 1.5 times that of the untreated fabric.

NORMAN G. TORCHIN, Primary Examiner.

MORRIS O. WOLK, Examiner.

H. WOLMAN, Assistant Examiner. 

1. IN THE PROCESS OF TREATING WITH ACID AQUEOUS FORMALDEHYDE SOLUTION A TEXTILE FABRIC PREPARED FROM POLYESTER BLEND YARNS, THE BLEND BEING A COMPOSITE OF 45% TO 80% SYNTHETIC LINEAR CONDENSATION POLYESTER FIBERS AND 20% TO 55% FIBERS OF THE GROUP CONSISTING OF CELLULOSE, WOOL AND NYLON FIBERS, THE IMPROVEMENT OF WETTING-OUT SAID FABRIC WITH AT LEAST 50%, BASED ON THE FABRIC WEIGHT, OF A HIGHLY ACID AQUEOUS SOLUTION CONTAINING AT LEAST 40 PARTS FORMALDEHYDE PER 100 PARTS BY WEIGHT OF SOLUTION AND SUFFICIENTLY STRONG, SOLUBLE, NON-OXIDIZING ACID TO HAVE A PH OF LESS THAN ABOUT 0.5, HEATING THE WET FABRIC FOR A PERIOD OF AT 